From: Joanne Koong <joannelkoong@gmail.com> mainline inclusion from mainline-v6.14-rc7 commit d9ecc77193cad25402ff5517fb26fb22b4db0e10 category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/ICJPON Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- There is a race condition leading to a kernel crash from a null dereference when attemping to access fc->lock in fuse_uring_create_queue(). fc may be NULL in the case where another thread is creating the uring in fuse_uring_create() and has set fc->ring but has not yet set ring->fc when fuse_uring_create_queue() reads ring->fc. There is another race condition as well where in fuse_uring_register(), ring->nr_queues may still be 0 and not yet set to the new value when we compare qid against it. This fix sets fc->ring only after ring->fc and ring->nr_queues have been set, which guarantees now that ring->fc is a proper pointer when any queues are created and ring->nr_queues reflects the right number of queues if ring is not NULL. We must use smp_store_release() and smp_load_acquire() semantics to ensure the ordering will remain correct where fc->ring is assigned only after ring->fc and ring->nr_queues have been assigned. Signed-off-by: Joanne Koong <joannelkoong@gmail.com> Link: https://lore.kernel.org/r/20250318003028.3330599-1-joannelkoong@gmail.com Fixes: 24fe962c86f5 ("fuse: {io-uring} Handle SQEs - register commands") Acked-by: Miklos Szeredi <mszeredi@redhat.com> Reviewed-by: Bernd Schubert <bschubert@ddn.com> Signed-off-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Long Li <leo.lilong@huawei.com> --- fs/fuse/dev_uring.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/fs/fuse/dev_uring.c b/fs/fuse/dev_uring.c index d2c374b2c220..55ecfda48f39 100644 --- a/fs/fuse/dev_uring.c +++ b/fs/fuse/dev_uring.c @@ -209,11 +209,11 @@ static struct fuse_ring *fuse_uring_create(struct fuse_conn *fc) init_waitqueue_head(&ring->stop_waitq); - fc->ring = ring; ring->nr_queues = nr_queues; ring->fc = fc; ring->max_payload_sz = max_payload_size; atomic_set(&ring->queue_refs, 0); + smp_store_release(&fc->ring, ring); spin_unlock(&fc->lock); return ring; @@ -1042,7 +1042,7 @@ static int fuse_uring_register(struct io_uring_cmd *cmd, unsigned int issue_flags, struct fuse_conn *fc) { const struct fuse_uring_cmd_req *cmd_req = io_uring_sqe_cmd(cmd->sqe); - struct fuse_ring *ring = fc->ring; + struct fuse_ring *ring = smp_load_acquire(&fc->ring); struct fuse_ring_queue *queue; struct fuse_ring_ent *ent; int err; -- 2.39.2